Integrated circuit technology is moving toward very dense large-scale integration which in turn can result in high power dissipation within a relatively small integrated circuit surface area. Particularly in the case of high frequency operation, it is desirable to keep interconnecting lead lengths very short, and the result compels high packing density of such circuits. In certain high power, high density circuits, power fluxes on the order of several hundred watts per square centimeter have been approached, and have taxed the capacity of heat sink technology to dissipate that heat and allow the associated semiconductor circuits to operate with a tolerable temperature rise. There is a need to increase the power flux handling capacity to the level of a kilowatt or more per square centimeter in some applications, and conventional techniques are limited in their ability to handle such high power densities.
Various forms of mechanical coolant systems have been devised in the past in an effort to remove heat from the heat-generating semiconductor source, and those systems have utilized both forced air and moving liquid. Among those techniques are microchannel cooling which utilizes an array of narrow channels either in the semiconductor substrate, or in a heat sink attached to the semiconductor substrate, and circulates cooling fluid through the microchannels for conducting heat away from the semiconductor device. While that approach has been found to be relatively efficient, it has heretofore been limited, using relatively conventional sources of cooling fluid, in its ability to operate at heat generating levels approaching 1000 watts per square centimeter while maintaining desirably low semiconductor junction temperatures. In short, the cooling efficiency is not as high as is desired to limit temperature to desired ranges in all forms of high power, high density integrated circuits.